Filter elements are used for filtering fluid flows or gaseous media. They are, for example, used for filtering an air flow that is guided into the passenger compartment of a motor vehicle. In this connection, an air-conditioning system built into the motor vehicle is in particular used to purify the outdoor air with respect to noxious substances, odors, etc., contained therein. In this context, appropriate filters or cabin air filters, respectively, are, for example, particle filters, odor filters or a combination thereof.
Furthermore, it is necessary to eliminate suspended matters from air that is supplied to an internal combustion engine. Such air filters, for example for trucks, construction machines, agricultural machines or even marine engines must be designed reliably and robustly, for they are exposed to extreme mechanical load during operation.
Filters are typically provided with a housing with a detachable housing cover, wherein a replaceable filter element can be mounted into the housing. Usually, the filter element has a tubular design and is fixed in the housing when the filter element is mounted into the housing.
DE 20 2007 002 906 U1 discloses a filter assembly in which a filter element is clamped by means of support knobs made of foam of polyurethane (PU), also called PUR foam, in a housing for the filter element.
However, the foam of polyurethane, i. e. the material of the support knobs, is released after heat storage (artificial storage) or temperature impact, respectively, or temperature change. In other words, the foam of polyurethane is force-free after heat storage. With the filter element held in the housing this leads again and again to the fact that in case of vibration excitation of the filter assembly and its parts, that is to say housing, filter element and housing cover, greater critical movements between individual parts occur. Such a vibration excitation may, for example, occur during the operation of a motor vehicle into which the filter assembly is built in.
EP 1 716 902 A discloses a filter assembly with a housing into which between housing and replaceable filter insert a spiral spring for clamping the filter insert is disposed.